Low emissivity and EMI shielding window films

ABSTRACT

A low emissivity and EMI shielding transparent composite film typically for use in association with window glazing and comprising a transparent film substrate having on one side thereof an underlayer of abrasion resistant hardcoat material with at least one infrared reflective layer covering the underlayer, typically a metallic layer which may be encased in metal oxide layers, which is then covered with a thin external protective top coat of a cured fluorinated resin.

CROSS REFERENCE TO RELATED APPLICATION(S)

This Application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/339,152, filed Mar. 1, 2010, the entiredisclosure of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure is related to the field of window films having lowemissivity (low e) for minimizing transfer of thermal energy byradiation, and that are suitable in electromagnetic interference (EMI)shielding applications.

2. Description of Related Art

Glass windows with a low emissivity (low e) are designed to allowfrequencies in a specific bandwidth to pass through the window, such asvisible light, while reflecting other frequencies outside of thisdesired bandwidth, such as infrared (IR). The low emissivity creates ahigh reflection of certain waves in the IR spectrum and serves toimprove the thermal insulation of windows in buildings and vehicles.Thus, these low e windows find particular use in cold climates forpreserving the heat in homes, offices, and automobiles and other heatedenvironments, mitigating the escape of the warm interior air to the coldexterior via the window. These low e windows are also useful in hotclimates for rejecting thermal energy radiation from the heated exteriorvia the window and thereby maintaining the cooler temperature of theinterior. These windows are effective in providing comfort, visibility,and increased energy efficiency.

Window glass itself may be manufactured to provide the low echaracteristics. During the manufacturing process and prior toinstallation, the glass is treated and/or coated with thin metalliclayers, among others, to achieve the desired IR reflection. Examples ofsuch treating and coating are described in U.S. Pat. Nos. 6,852,419 and7,659,002. This treated glass, however, is problematic for severalreasons. Firstly, it generally does not provide adequate protectionagainst ultraviolet (UV) radiation. Secondly, the metal or other coatingmay not be sufficiently protected against the environment, resulting ina decreased mechanical strength and subjecting the glass to corrosion.In this regard, if or when the glass corrodes or breaks, the entirewindow must be replaced. Not only is this costly, but it can also bedifficult to match the appearance and color of the original surroundingglass windows.

A more practical and economically efficient approach has been to utilizeflexible polymeric films that can be adhered to the window glass. Suchfilms are in widespread use and provide a variety of solar controlfunctions. The films are easy to apply, can conveniently be removed andreplaced, and can readily be made to duplicate the color and appearanceof the film that is being replaced. Also, flexible films facilitateretrofitting of existing clear glass window panes and can impart solarcontrol functions to the same. In this regard, the polymeric films alsosupply a level of protection from UV damage to household items, forexample, fading of furniture.

The majority of solar control films are made by metalizing a polymericsubstrate film, usually poly(ethylene terephthalate) (PET), and thenlaminating a second film of PET onto the metalized surface of thesubstrate film. These prior solar control films, however, sacrificevisible light transmittance (i.e., the amount of visible light thatpasses through the film, “VLT”) to achieve the desired emissivity, orvice versa, and have been limited to emissivities on the order of about0.3, at best.

An example of such low e window film (on the order of about 0.3) isdisclosed in U.S. Pat. No. 6,030,671. This and other previous low ewindow films utilize a metallic layer to reflect the IR radiation;however, metal is susceptible to corrosion, scratching, and abrasion.Thus, in such an application, a protective hardcoat is placed over themetal layers and facing the interior space to be reflected (i.e., theinterior of the room). This protective hardcoat is a conventionalcross-linked acrylate polyester based coating, and is necessary tosupply the film with resistance to cracking, corrosion, scratching, andabrasion.

Since this hardcoat is IR absorbing and located between the IRreflective metallic layer and the interior of the room, it decreases thecomposite emissivity of the film. Thus, the hardcoat thickness resultedin a compromise between being sufficiently thick to function as aprotective coat, whilst keeping IR absorption to a minimum. In anyevent, the hardcoat generally did not provide sufficient abrasionresistance, and when the hardcoat was thick enough to supply the filmwith the necessary durability, there remained serious detrimentaleffects on the emittance values. For example, U.S. Pat. No. 6,030,671describes the thickness of hard coat placed over the optical layers(i.e., the PET and metallic layers) as being between 1-3 microns, and ahardcoat having a thickness of 3.0 microns will result in film compositehaving an emissivity of greater than 0.35. Additionally, in order toachieve this composite emissivity of the film, the visible lighttransmittance (VLT) was limited to about 50%.

In addition to managing IR radiation, there exists a need to controlelectromagnetic radiation. Electromagnetic radiation of variousfrequencies is radiated from many devices used in a wide range offacilities including homes, workplaces such as offices, manufacturingand military installations, ships, aircraft and other structures.Examples of such devices include computers, computer monitors, computerkeyboards, radio equipment, communication devices, etc. If thisradiation escapes from the facility, it can be intercepted and analyzedfor the purpose of deciphering data associated with or encoded in theescaped radiation. For example, technology exists for reconstructing theimage appearing on a computer monitor in a building from a remotelocation outside the building or from a location within a building bydetecting certain wavelength frequencies from the monitor screen even ifthe monitor screen is not in view from the remote location. This isaccomplished by known techniques wherein certain frequencies of lightfrom the monitor screen, even after being reflected from varioussurfaces inside the building or room where the monitor is located,escape and are intercepted and analyzed by an eavesdropper in anotherlocation outside the building or room where the monitor is located.Obviously, the ability of an eavesdropper to intercept such radiationconstitutes a significant security risk, which is desirably eliminatedfrom facilities where secrecy is essential.

Although walls, such as brick, masonry block or stone walls mayeffectively prevent the escape of light frequencies from a facility,radio frequencies pass through walls that are not properly shielded toprevent such passage. Moreover, windows allow the passage of radiationto the outside where it can be intercepted, and can permit entry ofvarious forms of radiation, such as laser beams, infrared, and radiofrequencies, into the facility. As a result, sensitive or secret datamay be gathered from within the structure.

Indeed, the United States Government has long been concerned by the factthat electronic equipment, such as computers, printers, and electronictypewriters, give off electronic emanations. The TEMPEST (an acronym forTransient Electromagnetic Pulse Emanation Standard) program was createdto introduce standards that would reduce the chances of leakage ofemanations from devices used to process, transmit, or store sensitiveinformation. This is typically done by either designing the electronicequipment to reduce or eliminate transient emanations, or by shieldingthe equipment (or sometimes a room or entire building) with copper orother conductive materials. Both alternatives can be extremelyexpensive.

The elimination of windows from a structure would obviously minimize theabove-noted security risk. The disadvantages of a windowless or enclosedstructure, however, are self-evident. It would be highly desirable,therefore, to prevent the escape of radiation associated with datathrough windows while allowing other radiation to pass through so thatthe enjoyment of the visual effects provided by the windows can beobtained without an undue security risk.

The need for reducing the undesirable effects of electromagneticradiation has led to the development of window filters and films toblock the transmission of unwanted electromagnetic interference (EMI).These EMI shielding films, however, generally do not have the desirablelow e and high VLT discussed above.

Given both the endless need to improve energy efficiency and theimportance of security in today's competitive marketplace, a film thatcould preserve both energy and electronic privacy while maintainingadequate protection from the exposed environment is needed.

SUMMARY OF THE INVENTION

Because of these and other problems in the art, described herein, amongother things is a low emissivity transparent composite film comprising:a transparent film substrate; an underlayer of abrasion resistanthardcoat material compatible with the transparent film substrate; and atleast one infrared reflective layer; the composite film having anemissivity of less than about 0.30 and wherein the underlayer isdisposed between the transparent film substrate and the infraredreflective layer.

In certain embodiments, the infrared reflecting layer can be comprisedof a metallic layer selected from the group consisting of aluminum,copper, gold, nickel, silver, platinum, palladium, tungsten, titanium,or alloys thereof. In another embodiment, the composite film furthercomprises a transparent protective top coat having a dried thickness ofless than about 0.5 microns and the protective top coat is disposed overthe infrared reflective layer.

The underlayer can have an abrasion delta haze of less than about 5percent. In some embodiments, the infrared reflective layer includes atleast one thin metal film capable of protecting the infrared reflectivelayer. In another embodiment, the thin metal film is comprised of ametal selected from the group consisting of nickel, chromium, nobium,platinum, cobalt, zinc, molybdenum, zirconium, vanadium and alloysthereof. In yet another embodiment, the thin metal film is comprised ofa nickel-chromium alloy.

The composite film may also include at least one spacer layer comprisedof a transparent conductive layer, a dielectric layer, or combinationsthereof. In one embodiment, the spacer layer comprises a materialselected from the group consisting of indium oxide, indium zinc oxide,or indium tin oxide.

The composite film may also include a plurality of thin spacer layersdisposed between a plurality of transparent conductive layers.

Also disclosed herein is a low emissivity transparent composite filmcomprising: a transparent film substrate; an underlayer of abrasionresistant hardcoat material compatible with the transparent filmsubstrate; and at least one infrared reflective layer; the compositefilm having an emissivity of less than about 0.25.

The composite film could also have emissivity of less than about 0.20.In one embodiment, the composite film has a visible light transmissionof up to about 75 percent.

The composite film could also have an emissivity of less than about0.10. In one embodiment, the composite has a visible light transmissionof about 28 percent to about 47 percent. In another embodiment, thecomposite film has a visible light transmission up to about 70 percent.

In certain embodiments, the abrasion resistant hardcoat material of thecomposite film is selected from the group consisting of highlycrosslinked polymer coatings, thermally cured acrylate coatings,thermally cured sol gel coatings based on silicates, titanates,zirconates, or mixtures thereof, hybrid organic-inorganic sol gelmaterials, thermally cured siloxane hardcoats, and thermally curedpolyacrylate coatings. In one embodiment, the underlayer is comprised ofan ultraviolet cured polyacrylate composition. In another embodiment,the underlayer is comprised of an ultraviolet cured polyacrylatecomposition containing metal oxide nanoparticles.

In other embodiments, the infrared reflecting layer may be comprised ofa metallic layer selected from the group consisting of aluminum, copper,gold, nickel, silver, platinum, palladium, tungsten, titanium, or alloysthereof.

A method of manufacturing of a low emissivity transparent composite filmis also disclosed. The method comprises the following steps: providing atransparent film substrate; mixing an abrasion resistant hardcoatmaterial comprising a polyacrylate composition to form a mixture;applying the mixture to one side of the transparent film substrate;curing the coated side of the substrate to form an underlayer; andsputtering an infrared reflecting layer on the underlayer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of one embodiment of a low emissivityand EMI shielding window film which includes a protective top coat, anadhesive layer, and a release liner.

FIG. 2 is a cross-sectional view of another embodiment of a lowemissivity and EMI shielding window film which includes a protective topcoat.

FIG. 3 is a cross-sectional view of another embodiment of a lowemissivity and EMI shielding window film which includes a protective topcoat.

FIG. 4 is a cross-sectional view of another embodiment of a lowemissivity and EMI shielding window film which includes a protective topcoat.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Described herein, among other things, are composite films which have asignificant reduction in emissivity compared to conventional windowfilms while also allowing a desirable level of visible lighttransmission (VLT), increasing resistance to abrasion and cracking, andshielding electromagnetic interference (EMI). In one embodiment, thiscomposite film is comprised of a transparent film substrate having onone side thereof an underlayer comprising an abrasion resistant curedacrylate resin and at least one infrared reflective layer covering theunderlayer.

The underlayer advantageously increases the mechanical strength and,surprisingly, the abrasion resistance of the composite film, even thoughthe underlayer is not on the exterior of the composite film. In otherwords, the underlayer is between the surface to which the composite isattached and the IR reflective layer; thus, the IR reflective layer ismore closely exposed to the area desired to reflected. Thus, if thecomposite film is placed on the interior of a window, the IR from theinterior of the room would not have to pass through the underlayer inorder to be reflected therefrom. Alternatively, if the composite film isplaced on the exterior of the window, again, the IR from the outside orexterior would not have to pass through the underlayer in order to bereflected therefrom. As a result, the emissivity (i.e., the ability toemit or radiate the IR) of the composite film can be greatly decreased.

The composite films are typically applied to the interior or exteriorsurface of a window, and preferably the interior. As used herein, the“top” is the side of the composite that is exposed to area desired to bereflected. In this regard, the emissivity of the film is a measurementof the emittance of IR energy from the “top” surface (e.g., the IRenergy reflected back into the room when placed on the interior of thewindow). The “bottom,” on the other hand, is the side of the compositethat is attached to the window. For purposes of this disclosure, itshould also be recognized that IR energy as used herein is generallydiscussing long wavelength IR radiation, which is more directlyassociated with heat than shorter wavelength IR radiation. However, anywavelength of IR radiation can be reflected.

It should be noted, however, that while the composite films are oftenspecifically discussed for use as window films in this application, itwould be understood by one of ordinary skill that numerous otherapplications are appropriate. For example, the composite film could beattached to the wall of a building or temporary structure for use as aninsulation layer or as a heat retaining layer to reflect heat back intoa room. In this regard, the composite film could be also be decoratedand attached to a wall to form a decorative layer over the wall. Thecomposite film could also be placed on the exterior of cold orrefrigerated space in order to keep heat from entering this space.Additionally, without the adhesive layer discussed below as part of thecomposite, the composite films could be employed in a roller form foruse as tents, awnings, shades, or blinds—suspended in proximity to awindow or skylight but not adhered thereto. For such applications, itmay be desirable to have a very low visible light transmission in orderto block as much light as possible while still reflecting and retainingheat interior to the composite film. The composite film with theadhesive layer could also be used in the air gap of insulated glazings.These additional uses are merely exemplary and are in no way limiting.Accordingly, it should be understood that when use as window film isdescribed in this application, other uses also apply, as would be knownto one of ordinary skill in the art.

In order to understand the composite film of the present disclosure, itis also important to have an understanding of the properties andcharacteristics associated with a composite film and the tests by whichthese properties and characteristics of a polymer interlayer sheet aremeasured. Emissivity is the relative ability of a material's surface toemit or reflect energy by radiation, such as IR radiation. Stateddifferently, thermal radiation heat transfer is reduced if the surfaceof a material has a low emissivity. It is the ratio of energy radiatedby a particular material to energy radiated by a black body at the sametemperature and is measured according to ASTM C1371-04A. The compositefilms of the present disclosure have an emissivity of: less than about0.38; less than about 0.35; less than about 0.3; less than about 0.25;less than about 0.2; less than about 0.17; less than about 0.15; lessthan about 0.1; less than about 0.07; less than about 0.03; about 0.2 toabout 0.3; about 0.07 to about 0.10; about 0.08; and about 0.17.

The percent total solar energy rejection (% TSER) is, as the nameimplies, the total solar energy (heat) rejected by the composite film.The higher the number, the more total solar energy (heat) that isrejected. It is calculated from optical and heat rejection properties ofcoated film measured on a Varian Analytical Cary 5 spectrophotometer inaccordance with ASTM E903-82, the reflection and transmission data beinganalyzed using parameters as described by Parry Moon in “ProposedStandard Solar-Radiation Curves for Engineering Use,” Journal of theFranklin Institute Vol. 230 pp 583-618 (1940), the entire disclosure ofwhich is hereby incorporated by reference.

The solar energy absorption is the percent of incident solar radiationthat is absorbed by the window film. The lower the number, the lesssolar radiation absorbed. The solar reflectance is the percent ofincident solar radiation that is reflected by the window film/glasssystem. The lower the number, the less solar radiation reflected. Boththe solar absorption and reflectance can be measured using the abovemethod for measuring percent total solar energy rejection.

The visible light transmission is the percent of total visible lightthat is transmitted through the window film/glass system. The lower thenumber, the less visible light transmitted. It is calculated using CIEStandard Observer (CIE 1924 1931) and D65 Daylight. The composite filmsof the present disclosure have a visible light transmission, dependingon the emissivity, of less than about 1%; about 2% to about 5%; about25% to about 50%; about 28.5% to about 47%; about 30% to about 45%;about 28.5%; about 47%; about 55%; up to about 70%; and up to about 75%.

Electrochemical impedance spectroscopy (EIS) is well known to one ofordinary skill in the art and has been applied to the study of corrosionfor many years and is an accurate method of measuring corrosion rates.As used herein, it is used to measure the resistance of the filmcomposite to corrosion under the influence of the Chloride ion of NaClsolutions. A high impedance value (measured in M Ohms) means lesscorrosion. The composite films of the current disclosure have animpedance values of about 3.0 M Ohms to about 13.8 M Ohms; about 5.0 MOhms to about 13.8 M Ohms; about 5.0 M Ohms to about 8.0 M Ohms; about3.0 M Ohms to about 6.2 M Ohms.

Corrosion can also be measured with salt spray testing, which provides acontrolled corrosive environment which is commonly utilized to producerelative corrosion resistance information for specimens of metals andcoated metals exposed in a given test chamber. This test is performed inaccordance with ATSM B117-09. After 1000 and 2000 hours, the compositefilm samples are then measured for corrosion by photography and imageanalysis. The level of corrosion is based on the following scale: 1=nocorrosion; 2=very light corrosion; 3=light corrosion; 4=moderatecorrosion; and 5=heavily corroded. The composite films disclosed hereinshowed no corrosion or very light corrosion.

The corrosion of the composite films can also be measured with a saltwater exposure test. The composite films are sprayed with a saltsolution, taped to the lid of a box of water, and aged in a 50° C. ovenfor several days. After 4, 7, and 10 days of aging, the samples wererinsed with tap water and examined for corrosion. The scale above forthe salt spray testing was also applied to these samples. After 4 daysof aging, the composite films had no corrosion (1). After 7 days ofaging, the composite films had very light to no corrosion. Finally,after 10 days of aging, the composite films had very light to lightcorrosion.

The Taber Abrasion Test is a commonly utilized test for window films andother films for glazing or display applications. This test uses a TaberAbrader in accordance with ASTM D 1044 using CS-T3 wheels each loaded to500 grams. As the wheels scratch and grind the surface, the films becomemore hazy. Thus, the delta haze is the measure of change in haziness ofa film after being subjected to the abrasion of the wheel. The resultsare quoted in delta haze value after 100 cycles of the wheel. Forexample, a polyester film will generally have a delta haze of aboutgreater than 30%. The composite films, and specifically the underlayers,of the current disclosure have an abrasion delta haze of less than about5%; about 3% to about 5%; and about 4.1%.

The Alcohol Abrasion Test (termed “Crock Test”) utilizes an SDL AtlasCrock Meter type M238BB. Pure (100%) Isopropyl Alcohol (IPA) was chosenas the testing cleaner fluid. A mechanical arm with a removable clothend is placed in contact with a sample film. The cloth is soaked in IPAand cycled back and forth repeatedly. The results are subjective and theproduct is viewed for abrasion damage or breakthrough to the IRreflective layer(s) after 50 cycle intervals. The level of abrasion isbased on the following scale: 1=no breakthrough; 2=very lightbreakthrough; 3=slight breakthrough; 4=50% breakthrough; and 5=greaterthan 50% breakthrough. The composite films disclosed hereinadvantageously showed slight, very slight, and no breakthrough.

The adhesion test was in accordance with ASTM D 3359. Tape (3M 810 and600 tape) was pressed onto the sample surfaces and left forapproximately 10 seconds and then pulled off at a 180° angle. Thesamples were not cleaned or marked prior to testing. Samples of hardcoatwere evaluated on a pass/fail determination.

The EMI shielding strength was evaluated according to ASTM D-4935, via afar field type test using a coaxial TEM cell. The test measures theability of the product to block electromagnetic radiation. The resultsare reported in decibels (dB), as are well known and commonly used. Themore negative the value of decibels, the more electromagnetic radiationthat is blocked. The composite films of the current disclosure have ashielding efficiency of about −23 dB (which corresponds to approximately99.5% of blocked electromagnetic radiation) and about −31 dB (whichcorresponds to approximately 99.9% of blocked electromagneticradiation). Stated differently, the composite films of the currentdisclosure can block up to about 99.9% of electromagnetic radiation andup to about 99.5% of electromagnetic radiation.

With reference to FIG. 1, there is shown an embodiment of a compositefilm (10) comprising a transparent polymeric film substrate (11) coatedon one side with an underlayer (12). The underlayer (12) is covered withan IR reflective layer (20). Although by no means necessary, the IRreflective layer (20) may additionally be covered by a protective topcoat (13). As noted above, the bottom of the composite film (10) wouldbe the side of the substrate without the underlayer (12) and the top ofthe composite film (10) would be the side exposed.

When used as an exterior or interior window film, or as insulationattached to a wall, the substrate (11) may additionally have provided onits bottom a means for adhering the substrate to a window. As shown inFIG. 1 for example, the composite (10) has an adhesive layer (14)provided on the substrate (11). The adhesive layer (14) can be comprisedof any adhesive that is suitable for bonding the substrate (11) to awindow, wall or any other substrate. When being bonded to a window,pressure sensitive adhesives are preferable, with an acrylic basedadhesive being particularly preferable. Gelva 263 (available from CytecIndustries) is an example of such an adhesive. The adhesive layer (14)may also have a release liner (15) attached thereto. The release liner(15) advantageously provides a release effect against the stickyadhesive layer (14). The release liner (15) in the depicted embodimentcan comprise any polyethylene terephthalate (PET) film with a siliconerelease coating that can be peeled from the adhesive layer (14) leavingthe adhesive layer (14) on the base substrate (11). Alternatively, theadhesive and release layers may comprise a clear distortion freeadhesive with a polypropylene liner.

The transparent film substrate (11) is comprised of a flexible,transparent, polyester film. The substrate (11) is preferably apolyethylene terephthalate (PET) or polyethylene naphthalate (PEN) filmabout 2 mil (0.05 mm) in thickness. Although by no means necessary, thePET or PEN film may be treated with a UV absorber so as to absorb up to99% of UV radiation. An example of such an ultraviolet (UV) absorberfilm is described in U.S. Pat. No. 6,221,112, the entire disclosure ofwhich is hereby incorporated by reference. Melinex® 454 or ST505polyester films (available from DuPont Teijin Films, “DuPont”) areexamples of such preferred films. Additionally, the film may have beensurface treated with chemicals to improve adhesion thereto.

The underlayer (12) supplies an intermediate layer between and is bondtogether with, the underlying substrate (11) and the overlying IRreflective layer (20), improving the robustness, hardness, anddurability of these underlying and overlying optical layers (i.e., thecomposite film (10)). Additionally, the IR reflective layer (20) oftenincludes metals that are prone to atmospheric corrosion; however, theunderlayer (12) provides a high level of durability in terms ofresistance to cracking even though the underlayer (12) does not coverthe IR reflective layer (20). As a result, the composite film (10) hasincreased mechanical strength and greater resistance to abrasion,cracking, and scratching without negatively impacting the emissivity.Stated differently, the underlayer (12) protects the metallic IRreflective layer (20) from susceptibility to abrasion and scratching.The underlayers of the current disclosure have an abrasion delta haze ofless than about 5%; about 3% to about 5%; and about 4.1%.

The underlayer (12) can be comprised of any hardcoat, as that term isreadily understood by one of ordinary skill, that is compatible with thesubstrate (11) and able to be applied to the surface thereof throughconventional roll-to-roll coating. Examples of such hardcoats, include,but are not limited to, highly crosslinked polymer coatings, thermallycured acrylate coatings, thermally cured sol gel coatings based onsilicates, titanates, zirconates, or mixtures thereof, hybridorganic-inorganic sol gel materials (for example, Ormocer® polymersavailable from Fraunhofer), and thermally cured siloxane hardcoats. Thethermal curing of the hardcoat, if applicable, can occur by heat, suchas in an oven, or by NIR heating.

A preferred underlayer (12) is a UV cured polyacrylate compositionwithout nanoparticles. A particularly preferred underlayer (12) is a UVcured polyacrylate composition containing nanoparticles and comprised ofthe following: acrylic based resin, metal oxide nanoparticles,crosslinking agent, photoinitiator, solvent, and surfactant. Asdiscussed more fully below, not all of these are necessary constituentsof the composition. Additionally, the compositions below discuss weightpercentages based on the inclusion of the solvent. The solvent is merelyadded to aid in the application of the wet underlayer (12) to thesubstrate (11) and, the solvent evaporates upon drying. Thus, as one ofordinary skill in the art would readily appreciate, the below describedweight percentages of the acrylics and nanoparticles, for example, couldvary depending on the amount and type of solvent included in the wetunderlayer (12) composition.

The acrylic based resin may include diacrylates such as hexanedioldiacrylate, tricyclodecane dimethanol diacrylate (available as SartomerSR833 from Sartomer LLC), and dioxane glycol diacrylate (available asSartomer CD536 from Sartomer LLC) or a mixture of diacrylates. Othersuitable acrylic based resins are urethane aliphatic acrylates (Ebecryl®8301). The underlayer (12) preferably comprises about 10 to about 60weight percent (wt %) acrylic based resin. As noted above, these weightpercentages include the addition of the solvent discussed below. Thus,in a final, dried form, the underlayer (12) could comprise about 40 wt %to about 99 wt % acrylic based resin.

The metal oxide nanoparticle fillers are typically silicon dioxide(SiO₂) and aluminum oxide (Al₂O₃). These nanoparticles are by no meansnecessary; however, the addition of the nanoparticles to the underlayer(12) improves the mechanical and physical properties of the compositefilm (10). Specifically, the nanoparticles increase the hardness andflexural modulus of the underlayer (12) and composite film (10). Thenanoparticles are distributed in a controlled manner to also provide alevel of fine surface roughness to the composite film (10). This surfaceroughness reduces blocking, assists in roll handling, and improvesadhesion to the IR reflective layer (20). Additionally, because thenanoparticles are very small (typically 50 nm or less average particlesize), they have low haze and absorption and thus do not have anysignificant deleterious effect on the clarity or transmission propertiesof the composite film.

SiO₂ nanoparticles are particularly preferable. They are added in theform of dispersions of nanoparticles in the acrylate monomers and/orurethane acrylate monomers and are available from a number of suppliers.Examples of these nanoparticles include Nanocryl® C140 and XP21/2135(available from Hanse Chemie), Highlink® NanO-G 103-53 (available fromClariant Corp.), FCS100 (available from Momentive PerformanceMaterials), and Ebecryl® 8311 (available from Cytec Industries). Thesenanoparticles generally have a particle size of 0.1 microns or less. Thenanoparticles remain stably dispersed during film forming, drying, andUV curing and do not make any significant contribution to haze orreduction in gloss. The underlayer (12) could comprise 0 wt % to about65 wt %, and preferably about 21 wt %. Again, in a final, dried form,after the evaporation of the solvent, the underlayer (12) could comprisedifferent amounts of nanoparticles, for example, preferably about 43 wt%.

The crosslinking agent induces the formation of covalent chemical bondsbetween the polymer chains of the acrylic based resin via crosslinkingof molecules or groups when the mixture is subject to UV or EBradiation. The crosslinking turns the mixture into a more solidifiedstate, provides the underlayer (12) with the high mechanical strengthand abrasion resistance, and improves adhesion to the IR reflectivelayer (20). Cross linking agents may include pentaerythritoltetraacrylates and triacrylates and mixtures thereof, or suitableurethane acrylates. The underlayer (12) in wet form (i.e., with solvent)preferably comprises about 16 wt % to about 40 wt % crosslinking agentand more preferably about 21 wt % crosslinking agent.

The photoinitiator is used to promote the polymerization reaction and toaid in forming the hardness of the underlayer (12). Any suitablephotoinitiator known to one of ordinary skill in the art may be used,including, but not limited to azobisisobutyronitrile and benzoylperoxide. Examples of photoinitiators are Irgacure® 184 and Irgacure®907 (available from Ciba Specialty Chemicals). The underlayer (12)preferably comprises about 2 wt % to about 7 wt % photoinitiator, about2 wt % to about 3.5 wt %, and more preferably about 3.5 wt %photoinitiator.

The solvent is added to thin the composition and to form a solution thatcan be more easily applied to the substrate (11). After drying, thesolvent evaporates from the solution such that the final driedunderlayer (12) may comprise little to no solvent. Suitable solventsinclude, but are not limited to, n-butyl acetate, isopropyl alcohol, andMEK (methylethyl ketone). The underlayer (12) preferably comprises about10 wt % to about 50 wt % solvent, and more preferably about 25 wt %solvent.

Many surfactants are possible, including those commonly used in coatingformulations for leveling on a film substrate. Suitable surfactantsinclude, but are not limited to: Ebecryl® 1360 (available from CytecIndustries); Byk 3570, Byk UV-3530, and Byk UV-3500 (available from BykChemie); and Tego Wet 270 and Tego Glide 432 (available from EvonikIndustries). The underlayer (12) preferably comprises about 0.1 wt % toabout 0.2 wt % surfactant, and more preferably about 0.11 wt %surfactant.

The above ingredients for the underlayer (12) composition are mixedtogether for coating the substrate (11) to a wet film thickness of about3 to about 6 microns using any suitable process known to one of ordinaryskill which coats evenly and levels smoothly, such as a reverse gravureprocess. After application to the substrate (11), the coating is driedin an oven and UV cured under lamps at a line speed of about 80 ft perminute. The final cured, dried underlayer (12) has a thickness of about1.5 microns to about 6 microns; more preferably about 2 microns to about5 microns; and most preferably about 2.5 microns. If the underlayer (12)is too thin, the composite film (10) would not have the desiredmechanical durability, hardness, or abrasion resistance, nor would thecomposite film (10) be able to withstand the typical stresses ofinstallation and lifetime use.

The IR reflective layer (20) overlays the underlayer (12) and may beapplied to the underlayer (12) by sputtering, as that process is wellunderstood by one ordinary skill in the art, or any suitable depositionapplication, including, for example, evaporation or any chemical orphysical deposition. The IR reflective layer (20) may be comprised ofany transparent metal layer(s) that is highly reflective in the IRrange. In the embodiment in FIG. 1, the IR reflective layer (20) is acore layer (16) comprised of a metallic layer selected from the groupconsisting of aluminum, copper, nickel, gold, silver, platinum,palladium, tungsten, titanium, or an alloy thereof. Gold and silver andalloys thereof are generally preferred. As discussed more fully below,the types and amounts of metal and metal alloys in the IR reflectivelayer can be manipulated to achieve the desired emissivity and VLT. Forexample, tungsten and titanium are more highly absorptive of light thansilver and gold and thus would be most useful for embodiments with lowerVLT.

Additionally, as would be readily appreciated by those of ordinary skillin the art, the layer reflecting the IR, the IR reflective layer (20) inFIG. 1, may be comprised of either a single layer of metal or conductivemetal oxide or a multi-layer stack of metal, metal oxide, and/or otheroptical layers, whether comprised of metal or otherwise. For example,transparent conductive layers or dielectrics layers can be used inconjunction with a core metallic layer to control the IR lightreflection and VLT and protect the core metallic layer againstcorrosion. Any transparent conductive layer, as that term is understoodin the art, would be suitable, including, but not limited to, IndiumZinc Oxide (IZO), Indium Tin Oxide (ITO), Antimony Tin Oxide (ATO),indium oxide, zinc oxide, tin oxide, and other metal oxides, or mixturesthereof. Many of these transparent conductive layers could also be usedas a dielectric layer, as that term is understood in the art, ifsufficiently thin. In this regard, any dielectric which is transparentto visible light is suitable, including, but not limited to, IZO, ITO,silicon dioxide, aluminum oxide, silicon nitride, or mixtures thereof.When a particular layer is comprised of a transparent conductive layer,dielectric layer, or mixtures thereof, it is referred to herein as a“spacer layer.” Examples of embodiments with the above describedmulti-layer stacks are shown in FIGS. 2-4 and discussed more fullybelow.

Hard ceramics such as silicon oxynitride (SiOxNy) and aluminumoxynitride (AlOxNy) could also be added to improve the mechanical andphysical properties of the film (10) without adverse effects on thethermal and optical performance. Alternatively, thicker layer ceramicsand/or metal oxides could also be applied in conjunction with or as partof the IR reflective layer (20) to create a particular color or level ofreflection, but because these layers are likely to be more absorptive,they could reduce the level of heat retention in cold climates. In thisregard, the types, amounts, and thicknesses of the layers of metal,metal alloys, metal oxides, and hard ceramics can be manipulated toachieve the desired emissivity, VLT, mechanical strength, and visualappearance.

The protective top coat (13) is transparent and seals the surface of thesputtered IR reflective layer(s) (20) and should be very thin (forexample, less than 0.5 microns), such that there is no significanteffect on the composite emissivity. In this regard, the protective topcoat (13) does not contribute to the hardness of the composite film (10)for resistance to scratching.

This protective top coat (13) is by no means necessary to achievedesirable levels of emissivity, VLT, and abrasion resistance, as one ofordinary skill in the art would readily appreciate. However, theprotective top coat (13) provides other added benefits to the compositefilm (10). For example, the top coat (13) prevents the ingress ofcontaminants, including, but not limited to, atmospheric contaminantssuch as gaseous sulphur compounds in polluted areas and chloride ionsfrom fingerprints. Without the addition of the top coat (13), thesecontaminants could harm the physical and/or mechanical properties of thecomposite film (10). The top coat (13) also acts as a chemical barrierfor the underlying IR reflective layer(s) and thereby may reducecorrosion and allow abrasives to slide over the surface without causingscratches. Additionally, in some embodiments, the top coat (13) may havelow surface energy and friction which aids in the installation andcleaning of the composite film (10). Specifically, squeegees or otherinstallation or cleaning devices are able to move more easily over thesurface composite film (10).

The benefits of the protective top coat (13) described above can beachieved without significantly affecting the emissivity of the compositefilm (10) because the underlayer (12) additionally provides many ofthese benefits previously required of the protective hardcoat (e.g.,abrasion resistance) and thus allows for the use of an extremely thinprotective layer. Other benefits not mentioned herein would be readilyrecognized by one of ordinary skill in the art.

The protective top coat (13) will generally comprise silicon in someform, including, but not limited to, polysilazane, fluoroalkyl silane,and fluoro silane. The protective top coat (13) could comprise, forexample, about 7 wt % to about 8 wt % polysilazane. An example of such apolysilazane is G-Shield™ (available from KiON Specialty Polymers).Alternatively, the protective top coat (13) could be comprised of eitherfluoroalkyl silane or fluorosilane in the following ranges: about 0.5 wt% to about 1.5 wt %; less about 0.5 wt %; and less about 1.50 wt %.Examples of such fluoroalkyl silanes or fluorosilanes are, respectively,Dynasylan® F8261 (available from Evonik Industries) and Fluorolink® S10(available from Solvay Solexis Spa of Italy). The protective top coat(13) could additionally comprise solvents, photo-acid catalysts,photoinitiators, and other additives such as repellants (e.g., Sivo®Clear available from Silanex AB).

Silicon based compounds, however, are by no means necessary, as one ofordinary skill in the art would readily recognize. Instead, theprotective top coat (13) is merely designed to treat the surface for thefilm and to provide the above described benefits without a significanteffect on emissivity. For example, finishes used for treating thesurface of glass, such as wax type coatings, and fluorocarbons used forsoil release may also be utilized.

One preferred protective top coat (13) is a UV or EB cured fluorinatedresin comprised of about 1.0 parts fluorosilane resin, about 0.5 toabout 1.5 parts photoinitiator, and about 97 to about 99 parts solvent,where the parts are parts by weight.

The solvent is added to thin the composition and to form a solution thatcan be more easily applied to the IR reflective layer (20). Afterdrying, the solvent evaporates from the solution such that the finaldried protective top coat (13) may comprise little to no solvent.Suitable solvents include, but are not limited to, isopropyl alcohol(IPA), glycol ether, butyl acetate, xylene, water, and any mixturesthereof. The composition can contain one or more of these solvents.Suitable fluorosilanes include, but are not limited to, fluoro alkylsilanes. An example of such a fluorosilane is a dispersion ofFluorolink® S10 (available from Solvay Solexis Spa of Italy). Preferredphotoinitiators include Cyracure™ 6976 (available from Dow Chemicals)and Chivacure® 1176 (available from Chitech).

A particularly preferred top coat composition comprises about 70 wt %IPA, about 20 wt % glycol ether, about 5.9 wt % water, about 1.48 wt %fluorosilane dispersion, and about 1.48 wt % photoinitiator. It shouldbe noted that when preferred compositions are discussed herein, thetotal composition may be greater than or less than 100 wt %. As one ofordinary skill in the art would readily recognize, this is merely areflection of the fact that the weight percents given are not exact andmay be rounded to reflect an approximate (or “about”) weight percent.Additionally, as noted above, the weight percentages discussed hereincould vary depending on the amount and type of solvent added, as one ofordinary skill in the art would readily appreciate.

The above ingredients for the protective top coat (13) composition aremixed together for coating the IR reflective layer(s) (20) to a wet filmthickness of about 1 micron to about 3 microns using any suitableprocess known to one of ordinary skill which coats evenly and levelssmoothly, such as, but not limited to, a reverse gravure process. Afterapplication to the PET film, the coating is dried in an oven at atemperature of about 80° C. to about 110° C. for 5 to 20 seconds. Theprotective top coat (13) is then UV cured at a running speed of about 20to 30 meters per second. The final cured, dried protective top coat (13)has a thickness of less than about 0.5 microns and preferably about 0.05microns.

With reference now to FIG. 2, the composite (110) is substantially thesame as the composite (10) excepting that the IR reflecting layer (120)is a multi-layer stack. In a preferred embodiment, the IR reflectinglayer (120) can comprise at least one core layer (116). The core layer(116) may be comprised of any metal that is highly reflective in the IRrange, including, but not limited to, a metallic layer selected from thegroup consisting of aluminum, copper, nickel, gold, silver, platinum,palladium, tungsten, titanium, or any alloy thereof. In a preferredembodiment, the core layer (116) is a gold-silver alloy having betweenabout 7 nm and about 35 nm in thickness, depending upon the requiredemissivity of the film (110). However, other metals or alloys discussedabove would also be suitable in this embodiment.

The IR reflecting layer (120) can also comprise a silicon based layer(114) adjacent and aiding in adhesion to the underlayer (12). Thesilicon based layer (114) can be comprised of silicon nitride, siliconoxide, or silicon oxynitride layer, preferably a silicon nitride, andhaving between about 1 nm and about 25 nm in thickness. The siliconbased layer (114) is covered by a thin metal film (115) having betweenabout 1 nm to about 5 nm in thickness. This thin metal film (115) servesto protect the core layer (116) and can be comprised of any metalselected from the group consisting of nickel, chromium, nobium, gold,platinum, cobalt, zinc, molybdenum, zirconium, vanadium, and alloysthereof. A nickel-chromium alloy is particularly preferred, such asHastelloy™ (available from Haynes International) or Inconel™ (availablefrom Special Metals Co.) and as described in U.S. Pat. No. 6,859,310,the entire disclosure of which is hereby incorporated by reference.

The IR reflective layer (116) is then covered by a second thin metalfilm (117), preferably nickel-chromium alloy, and having between about 1nm to about 5 nm in thickness. The second thin metal film (117) is inturn covered by a spacer layer (118) having between about 40 and about80 nm in thickness. As noted above, the spacer layer is comprised of anytransparent conductive layer, dielectric layer, or combinations thereof.The spacer layer (118) is preferably a transparent conductive layercomprised of ITO. The spacer layer (118) is then covered by a secondsilicon based layer (119) formed from one of silicon nitride, siliconoxide, or silicon oxynitride and having between about 1 to about 25 nmin thickness. This silicon based layer (119) is then coated with theprotective top layer (13). The layers ((114) to (119)) are formed bysputtering as is well known in the art.

With reference now to FIG. 3, the composite film (210) is substantiallythe same as the composite (10) excepting that the IR reflecting layer(220) is a multi-layer stack comprised of a core layer (216) encased ina multi-layer stack and sandwiched between two spacer layers ((214) and(218)), comprised of any transparent conductive layer, dielectric layer,or combinations thereof, as described above. The IR reflecting layer(220) is made up of a first spacer layer (214) adjacent to theunderlayer (12) and having about 45 nm in thickness. The first spacerlayer (214) is then covered by a core layer (216) having about 12 nm inthickness depending upon the required emissivity of the composite film(210). Again, the core layer (216) may be comprised of any metal that ishighly reflective in the IR range, including, but not limited to, ametallic layer selected from the group consisting of aluminum, copper,nickel, gold, silver, platinum, palladium, tungsten, titanium, or anyalloy thereof. In this embodiment, the core layer (216) is preferablypure gold or a gold alloy where gold is the major constituent. The corelayer (216) is then covered by a second spacer layer (218) having about35 nm in thickness, which is in turn covered by silicon based layer(219) having 10 nm in thickness and comprising silicon nitride orsilicon aluminum nitride. The layers ((214), (216), (218), and (219))are formed, for example, by sputtering. The silicon based layer (219) isthen coated with the protective top coat (13).

With reference now to FIG. 4, the composite (310) is substantially thesame as the composite (10) excepting that the IR reflecting layer (320)is now provided by a multi-layer stack comprised of a plurality oftransparent conductive layers ((314), (316), and (318)) which serve asIR reflectors and are preferably comprised of IZO, interleaved by thinmetal oxide layers ((315) and (317)), which introduces flexibility tothe composite (310). The thin metal oxide layers ((315) and (316)) arepreferably, but by no means necessarily, comprised of nickel-chromiumoxide. For example, the thin metal oxide layers ((315) and (316)) couldalternatively be comprised of a spacer layer, as that term is definedabove. The IR reflecting layer (320) is located over the underlayer (12)and may be provided with a protective top coat (13).

Preferably, the infrared reflective layer includes a plurality of thinspacer layers disposed between a plurality of transparent conductivelayers wherein there is one more transparent conductive layer thanspacer layer. This arrangement, however, is by no means necessary. Thenumber of transparent conductive layers and spacer layers (or thin metaloxide layers) may be varied depending upon the required flexibility ofthe IR reflecting layer (320) and the total thickness of the transparentconductive layers in the IR reflecting layer (320) will generallydetermine the emissivity, with the total thickness of the transparentconductive layers generally being above about 200 nm. In any event, thetotal thickness of transparent conductive layers and interleaving spacerlayers should preferably not exceed 260 nm in thickness, although thisis by no means necessary, as one of ordinary skill in the art wouldreadily appreciate.

In one embodiment, the IR reflecting layer (320) is made up of a firsttransparent conducting layer (314) adjacent to the underlayer (12) andhaving about 65 nm, a first thin metal oxide layer (315) having about 5nm in thickness and covering the first transparent conducting layer(314), a second transparent conducting layer (316) having about 65 nm inthickness and covering the first thin metal oxide layer (315), a secondthin metal oxide layer (317) having about 5 nm in thickness and coveringthe second transparent conducting layer (316), and a third transparentconducting layer (318) which is optionally coated with the protectivelayer (13). The layers ((314)-(318)) are formed by sputtering as is wellknown in the art.

Composite films as shown in FIGS. 1-4 may be utilized on the interior orexterior of window glazings including vehicles and buildings. Thecomposite films may be used with single pane windows or with dual ortriple pane windows and will improve the U-Factor of a window. TheU-Factor measures the rate of heat transfer or loss through a window aslaid down by the National Fenestration Rating Council. Additionally, anyand all embodiments of the composite films may be provided with orwithout the adhesive layer and release liner.

The embodiments described above provide an improved low emissivitycomposite combining the desirable properties of exceptionally lowemissivity with abrasion and scratch resistance. For example,embodiments disclosed herein have a VLT between about 28.5% and about47% with a very low emissivity of about 0.1 or less. Such an embodimentmay be desirable in warmer sunny climates. Another embodiment disclosedherein may have a higher VLT, up to about 75% for example, with anemissivity of about 0.20 or less. Such an embodiment may desirable, forexample, in cooler, northern climates. Additionally, the embodimentsdescribed above effectively reduced EMI. For example, embodimentsdisclosed herein have an EMI shielding value of about −23 dB and about−31 dB.

The presently described composite films will now be described withreference to the following non-limiting examples.

EXAMPLES 1-2

Composite films “Sample A” and “Sample B” were constructed in accordancewith FIG. 2 and as described above with the following layers andthicknesses shown in Table 1.

TABLE 1 Layer (Referenced Sample A Sample B to FIG. 2) Layer TerminologyComposition Thickness Thickness 11 Transparent Film Polyethyleneterephthalate (PET) 2 mil 2 mil Substrate 12 Underlayer UV curedpolyacrylate 2.5 microns 2.5 microns composition containing metal oxidenanoparticles 114 Silicon Based Silicon nitride 15 nm 15 nm Layer 115Thin Metal Film Nickel-chromium (Ni—Cr) 2 nm 2 nm 116 Core LayerSilver-gold alloy (Ag—Au) 15 nm 25 nm 117 Second Thin Metal Ni—Cr 2 nm 2nm Film 118 Spacer Layer Indium Tin Oxide (ITO) 55 nm 60 nm 119 SecondSilicon Silicon nitride 10 nm 15 nm Based Layer 13 Protective Top UVcured fluorosilane 0.05 microns 0.05 microns Coat composition

Samples A and B were then tested for optical and physical propertiesaccording to the above testing methods. The results are given below inTable 2.

TABLE 2 Sample A Sample B VLT 47% 28.5%   Emissivity 0.10 0.07 TotalSolar Energy 66% 79% Rejection (TSER) Absorption 19% 21% Reflection ofvisible light 37% 62% from front top coat (% R) Reflection of visiblelight 20% 56% from rear PET face (% R) Total Solar Transmission 14% 18%Solar Energy Reflected 50% 62% Externally Solar Energy Reflected 53% 56%Internally Adhesion Pass Pass Crock Test 1   1   EMI Shielding N/A −31dB

EXAMPLES 3-5

Sample A was also tested for comparison with various similar samples.Sample A is designed as described above in Example 1 with an untreatedPET film layer. Sample C provides for the same stack design as Sample A,except that the PET film is treated and the underlayer was omitted.Sample D provides for the same stack design as Sample A (with anuntreated PET film layer), except that the underlayer was omitted.Sample E provides for the same stack design as Sample A, except that theprotective top coat was removed. The test results are shown below inTable 3.

TABLE 3 Sample A Sample C Sample D Sample E Crock Test Pass Fail Fail 5%Removal Tape Adhesion Pass Pass Pass Fail Taber (Δ Haze %) 3.0-5.0 — — —EIS (Impedance 3.0-6.2 — — — in M Ohms)

The results in Table 3 demonstrate that without the supportingunderlayer, the composite samples fail the Crock Test. Surprisingly, thepresence of the abrasion resistant underlayer affects the resistance ofthe protective top coat and IR reflective layers to damage.

EXAMPLES 6-7

Composite films “Sample F” and “Sample G” were constructed in accordancewith FIG. 3 and FIG. 4, respectively, and as described above with thefollowing layers and thicknesses shown in Tables 4-5.

TABLE 4 Layer (Referenced Layer Sample F to FIG. 3) TerminologyComposition Thickness 11 Transparent Polyethylene 2 mil Filmterephthalate (PET) Substrate 12 Underlayer UV cured polyacrylate 2.5microns composition containing metal oxide nanoparticles 214 FirstSpacer Indium Zinc Oxide (IZO) 45 nm Layer 216 Core Layer Gold or goldalloy where 12 nm gold is the major constituent 218 Second Spacer IZO 35nm Layer 219 Silicon Base Silicon nitride or silicon 10 nm Layeraluminum nitride 13 Protective Top UV cured fluorosilane 0.05 micronsCoat composition

TABLE 5 Layer (Referenced to Sample G FIG. 4) Layer TerminologyComposition Thickness 11 Transparent Film Polyethylene 2 mil Substrateterephthalate (PET) 12 Underlayer UV cured 2.5 microns polyacrylatecomposition containing metal oxide nanoparticles 314 First TransparentIndium Zinc 65 nm Conductive Layer Oxide (IZO) 315 First Thin MetalNickel-Chromium 5 nm Oxide Layer Oxide 316 Second IZO 65 nm TransparentConductive Layer 317 Second Thin Metal Nickel-Chromium 5 nm Oxide LayerOxide 318 Third Transparent IZO 65 nm Conductive Layer 13 Protective TopUV cured 0.05 microns Coat fluorosilane composition

Samples F and G were then tested for optical and physical propertiesaccording to the above testing methods. The results are given below inTable 6.

TABLE 6 Sample F Sample G VLT 70% 75% Emissivity 0.08 0.17 Total SolarEnergy 50% 27% Rejection (TSER) EMI Shielding −23 dB N/A

EXAMPLES 8-13

Protective top coats “Sample H,” “Sample I,” “Sample J,” “Sample K,”“Sample L,” and “Sample M” were constructed in accordance with thedescriptions above with the following compositions (based on weightpercentages) as shown in Table 7.

TABLE 7 Generic Top Coat Description Formulation Sample H Sample ISample J Sample K Sample L Sample M Solvent IPA 97 38 99 97 — 36 SolventGlycol Ether — 60 — — — 36 PM Solvent Butyl Acetate — — — — 93 — SolventXylene — — — — — 4.7 Solvent DI H₂O 2 1.8 — 2 — — PolysilazaneG-Shield ® — — — — 7.4 — Fluoroalkyl Dynasylan ® — — — 0.53 — —Bifunctional F8261 Silane Fluoro Silane Fluorolink ® 0.52 0.44 0.54 — —0.26 S10 Repellant Sivo Clear ® K1 — — — — — 12 Repellant Sivo Clear ®K2 — — — — — 12 Photoinitiator Cyracure ™ 0.52 — — — — —

Samples H-M were then tested for optical and physical propertiesaccording to the above testing methods. The results are given below inTable 8.

TABLE 8 Testing Method Parameters Sample H Sample I Sample J Sample KSample L Sample M Salt Spray After 1000 1 1 1 1 1 1 Testing hours (basedon 50 After 2000 4 1 1 1 3 1.5 square centimeter hours testing area) EISEquivalent M Ohms 10 7.5 5 8 7.5 13.8 Circuit Salt Water After 4 days 11 1 1 1 1 Exposure Test After 7 days 1 1 1 1 2 1 After 10 days 2 3 3 3 23

As noted above, the level of corrosion for the Salt Spray Testing andthe Salt Water Exposure is based on the following scale: 1=no corrosion;2=very light corrosion; 3=light corrosion; 4=moderate corrosion; and5=heavily corroded.

EXAMPLES 13-18

Underlayers “Sample N,” “Sample O,” “Sample P,” “Sample Q,” “Sample R,”and “Sample S” were constructed in accordance with the descriptionsabove with the following compositions (based on weight percentages) asshown in Table 9.

TABLE 9 Generic Top Coat Description Formulation Sample N Sample OSample P Sample Q Sample R Sample S Solvent n-Butyl Acetate 25 25 25 2525 25 Photoinitiator Irgacure ® 184 2.80 1.67 2.85 2.85 2.85 1.67Photoinitiator Irgacure ® 907 0.70 0.33 0.71 0.71 0.71 0.33 Resin SR83317.5 7.2 10.7 10.7 10.7 9.1 Resin Ebecryl ® 8301 23 — — — — 25 MercaptoTMPMP — 3.6 — — — 3.6 Propionate Surfactant 50% Byk 3570 0.14 0.22 0.210.21 0.21 0.22 Nanoparticle Ebecryl ® 8311 — 43 43 25 43 — NanoparticleNanocryl ® C140 — — — — 18 25 Nanoparticle FCS100 — 18 18 18 — —Nanoparticle XP 21/2135 — — — 18 — 9 Nanoparticle Highlink ® 32 — — — —— NanO-G 103-53

Samples N—S were then formed with the IR reflective layer(s) asdescribed above and with the above methods. Additionally, Samples N—Swere then prepared with and without the protective top coat (Sample H)were then tested for abrasion resistant according to the above describedCrock testing methods. The results are given below in Table 10.

TABLE 10 Sample N Sample O Sample P Sample Q Sample R Sample S Abrasion4 3 5 4 2 2 Without Protective Top Coat Abrasion 2 2 3 4 1 1 WithProtective Top Coat (Sample H)

As noted above, the level of abrasion is based on the following scale:1=no breakthrough; 2=very light breakthrough; 3=slight breakthrough;4=50% breakthrough; and 5=greater than 50% breakthrough. The aboveresults demonstrate that the underlayer alone, without a protective topcoat, can provide sufficient, very light abrasion resistance.Additionally, the results demonstrate that the protective top coats ofthe current disclosure can provide a certain added level of abrasionresistance.

While the invention has been disclosed in conjunction with a descriptionof certain embodiments, including those that are currently believed tobe the preferred embodiments, the detailed description is intended to beillustrative and should not be understood to limit the scope of thepresent disclosure. As would be understood by one of ordinary skill inthe art, embodiments other than those described in detail herein areencompassed by the present invention. Modifications and variations ofthe described embodiments may be made without departing from the spiritand scope of the invention.

It will further be understood that any of the ranges, values, orcharacteristics given for any single component of the present disclosurecan be used interchangeably with any ranges, values or characteristicsgiven for any of the other components of the disclosure, wherecompatible, to form an embodiment having defined values for each of thecomponents, as given herein throughout. Further, ranges provided for agenus or a category, such as dielectric metal oxides, can also beapplied to species within the genus or members of the category, such asIZO, unless otherwise noted.

The invention claimed is:
 1. A low emissivity transparent composite filmcomprising: a transparent film substrate; an underlayer of abrasionresistant hardcoat material deposited on the surface of the filmsubstrate and comprising a crosslinked acrylate polymer and metal oxidenanoparticles, the underlayer having a dried thickness of about 2 toabout 6 microns; at least one infrared reflective layer; and atransparent, protective top coat disposed over the infrared reflectivelayer, the protective top coat having a thickness of less than 0.5microns and comprising a polysilazane, fluoro silane, fluoroalkylsilane, or combination thereof; wherein the composite film has anemissivity of less than about 0.30.
 2. The composite film of claim 1wherein the infrared reflecting layer comprises at least one metalliclayer selected from the group consisting of aluminum, copper, gold,nickel, silver, platinum, palladium, tungsten, titanium, and alloysthereof.
 3. The composite film of claim 2 wherein the infraredreflective layer comprises at least one spacer layer comprising atransparent conductive layer, a dielectric layer, or combinationsthereof.
 4. The composite film of claim 3 wherein the spacer layercomprises at least one metal oxide selected from the group consisting ofindium oxide, indium zinc oxide, and indium tin oxide.
 5. The compositefilm of claim 1, wherein the underlayer has an abrasion delta haze of 5percent or less.
 6. The composite film of claim 1 wherein the infraredreflective layer comprises at least one thin metal film capable ofprotecting the infrared reflective layer.
 7. The composite film of claim6 wherein the thin metal film comprises at least one metal selected fromthe group consisting of nickel, chromium, nobium, platinum, cobalt,zinc, molybdenum, zirconium, vanadium and alloys thereof.
 8. Thecomposite film of claim 7 wherein the thin metal film comprises anickel-chromium alloy.
 9. The composite film of claim 1 wherein theinfrared reflective layer comprises a plurality of thin spacer layersdisposed between a plurality of transparent conductive layers.
 10. A lowemissivity transparent composite film comprising: a transparentpolyester film substrate; an underlayer of abrasion resistant hardcoatmaterial deposited on the surface of the film substrate and comprising acrosslinked acrylate polymer and about 21 to about 65 weight percent ofmetal oxide nanoparticles, the underlayer having a dried thickness ofabout 2 to about 6 microns and an abrasion delta haze of about 3 toabout 5%; at least one infrared reflective layer; and a transparent,protective top coat disposed over the infrared reflective layer, theprotective top coat having a thickness of less than about 0.5 micronsand comprising a polysilazane, fluoro silane, fluoroalkyl silane, orcombination thereof; wherein the composite film has an emissivity ofless than about 0.25.
 11. The composite film of claim 10 which has anemissivity of less than about 0.20.
 12. The composite film of claim 11which has a visible light transmission of up to about 75 percent. 13.The composite film of claim 10 which has an emissivity of less thanabout 0.10.
 14. The composite film of claim 13 which has a visible lighttransmission of about 28 percent to about 47 percent.
 15. The compositefilm of claim 13 which has a visible light transmission up to about 70percent.
 16. The composite film of claim 10 wherein the metal oxidenanoparticles comprise silicon dioxide, aluminum oxide, or a combinationthereof.
 17. The composite film of claim 10 wherein the infraredreflecting layer comprises at least one metallic layer selected from thegroup consisting of aluminum, copper, gold, nickel, silver, platinum,palladium, tungsten, titanium, and alloys thereof.
 18. A method ofmanufacturing the low emissivity transparent composite film of claim 1,comprising: coating a mixture of an abrasion resistant hardcoat materialcomprising a polyacrylate polymer and metal oxide nanoparticles to oneside of a transparent film substrate; curing the coated side of the filmsubstrate to form an underlayer having a dried thickness of about 2 toabout 6 microns; sputtering an infrared reflecting layer on theunderlayer; and applying a transparent, protective top coat over theinfrared reflective layer, the protective top coat having a thickness ofless than 0.5 microns and comprising a polysilazane, fluoro silane,fluoroalkyl silane, or combination thereof; wherein the composite filmhas an emissivity of less than about 0.30.